Toyota RAV4 Forums banner

1 - 20 of 221 Posts

·
Registered
Joined
·
342 Posts
Discussion Starter #1
Blocking the engine radiator in cold weather is a century old trick. It helps both non-hybrid and hybrid vehicles. But hybrids especially since the engine can be off 50%+ of the time in city driving.

In the RAV4, even in not that cold weather (25-32F), I observed coolant temperature drop below 150F when sitting at long traffic lights or driving down slight hills for a few minutes. That is really cold for an engine that has a 180F thermostat. The engine comes on much more often just to heat up the cabin.

Some newer vehicles made in the last few years have active grille technology that regulates air flow over the radiator depending on the engine cooling needs. But this technology is not available on the RAV4, yet.

So if you trust yourself to remember to take off any grille blocking if it suddenly warms up, you can safely block at least 50% of the grille area if it's below 40F outside.
 

·
Registered
Joined
·
1,992 Posts
5MPG is an exaggeration. While its true that radiator blocking helps maintain engine temps, on the Rav it will be more like 1-2MPG than 5. And it doesn't change the severe hit you see from short trips. A Prius might see that amount of increase on longer trips.
Also good to note that active shutters are mechanical, and a failure of that mechanism results in an un-drivable car.
 

·
Registered
Joined
·
428 Posts
So I lost apx. 1 MPG in mileage this winter but I get 5 MPG back? Dang, where do I sign up for that? After 10 years I should be up to 70 MPG!!
Much of the mileage difference is cooler denser air = more resistance, wet roads = more resistance, winter blend fuels = worse mileage. So IMO, I possibly lost 1/2 mpg due to longer warmup times.
 

·
Registered
Joined
·
422 Posts
I went from 42mpg to 34mpg. Most is lost because the ICE have to be running very often to produce heat for the cabin.


Skickat från min iPhone med Tapatalk
 

·
Registered
Joined
·
342 Posts
Discussion Starter #7
Did you try it out? I'm not gonna do it but I'm curious.
Yes. I used to do many years ago when I was living up north near the Canadian border. In the winter time, it would take 10 miles to warm an engine fully, and at highway speeds the engine would drop 20-30F below the 190F design temperature. This was a pure gasoline large engine 4x4 truck.

And I have tried it 2 weeks ago on the RAV4. So far I blocked only the grille between the headlights, not the lower grille in the bumper. The lower is much larger actually. This helped with MPG greatly.

There is a 20 miles route that I take regularly, with about a 35mph average speed. In the warmer weather I got a consistent 44 to 44.5 MPG. When the temps dropped to around the freezing mark, and I started using cabin heat, MPG dropped to 35 to 35.5 MPG on the same route. With the upper vents blocked I'm back to 40-41 MPG.

But when I look at coolant temperature through OBDII, the engine still does not make enough heat from propelling the vehicle, as coolant sometimes drops into 150-160F range. This is telling me that more grille area can be blocked.

Everyone's mileage will vary, as they say. It depends how much grille area is block, what the outside temps are, the length of trip and type of driving. But you will never know until you try. :D

I would be very curious to see what improvement you get in the much colder climate than I am. You can Google "vent blocking prius". There is a lot of information about this practice.
 

·
Registered
Joined
·
846 Posts
Blocking the engine radiator in cold weather is a century old trick. It helps both non-hybrid and hybrid vehicles. But hybrids especially since the engine can be off 50%+ of the time in city driving.

In the RAV4, even in not that cold weather (25-32F), I observed coolant temperature drop below 150F when sitting at long traffic lights or driving down slight hills for a few minutes. That is really cold for an engine that has a 180F thermostat. The engine comes on much more often just to heat up the cabin.

Some newer vehicles made in the last few years have active grille technology that regulates air flow over the radiator depending on the engine cooling needs. But this technology is not available on the RAV4, yet.

So if you trust yourself to remember to take off any grille blocking if it suddenly warms up, you can safely block at least 50% of the grille area if it's below 40F outside.
Can you share some photos and specific materials you used?
 

·
Registered
Joined
·
342 Posts
Discussion Starter #9
Can you share some photos and specific materials you used?
Since my RAV4 is black, I cut a strip of plastic from a heavy duty black trash bag. About 2" x 32". Then I used some black electrical tape to tape it into place. I did this just to see what happens, not expecting to see such large gains.

But now I think I'll keep it as is for the season. The tape seems to be holding up and it looks ok since everything is black. I can take a picture if you are still interested. :D

I'll try blocking half of the lower grille next.
 

·
Registered
Joined
·
422 Posts
I would like a picture if possible. Be careful with those cooler fins they are usually fragile.


Skickat från min iPhone med Tapatalk
 

·
Registered
Joined
·
342 Posts
Discussion Starter #11
I would like a picture if possible.
Here you go.

Another idea is try to drive with the recirculate on, and see what kind of improvement you get. If you can put up with windows fogging up, and MPG goes up significantly, investing in some plastic and tape will pay off quickly given that gasoline is $5+ per gallon in Europe. :D
 

Attachments

·
Registered
Joined
·
422 Posts
Here you go.

Another idea is try to drive with the recirculate on, and see what kind of improvement you get. If you can put up with windows fogging up, and MPG goes up significantly, investing in some plastic and tape will pay off quickly given that gasoline is $5+ per gallon in Europe. :D
Thanks. I googled "vent block prius" and found some nice info.

I'm gonna try the mod tomorrow, I keep good track of my MPG's.

Did you already notice any improvement?
 

·
Member-RAV4 ReGeneration
Joined
·
264 Posts
I live in a fairly mild climate, with moderate winters, but in the past, I regularly blocked the radiator of my Prius, with cardboard, in the winter. I would estimate a 2-3 mpg improvement, but saw the biggest improvement in increased cabin heat. I have not tried this with my RAV4H yet, but did notice engine temperature drops, with temps here in the low 20's, when just idling. Hard to believe someone has not seen this as a business opportunity yet.
 
  • Like
Reactions: Torque

·
Premium Member
Joined
·
7,936 Posts

·
Premium Member
Joined
·
7,936 Posts
I thought about using black Gorilla tape, but it might leave sticky residue which I don't want to deal with come warmer weather, will be using zip ties.
 

·
Member-RAV4 ReGeneration
Joined
·
264 Posts
I thought about using black Gorilla tape, but it might leave sticky residue which I don't want to deal with come warmer weather, will be using zip ties.
Yes, zip ties are the way to go. I just clipped the zip ties and reused the same cardboard every year. Personally, I have concerns about tape on the paint for expended periods.
 

·
Registered
Joined
·
342 Posts
Discussion Starter #18
Did you already notice any improvement?
Yes, noticed it immediately on the 1st drive. I have a regular route where I lost 9 MPG when temps went down from 50's in Fahrenheit to around freezing. Before the plastic on the grille the engine used to turn off at traffic lights, but came on immediately when moving. There was almost no battery only drive. And the coolant temp needle could not stay in the middle.

With the plastic I'm getting much more battery only drive. I can now again accelerate up to 25-30 MPH on battery only and then the gas engine picks up. And picked up 5-6 MPG.

The real cold weather is coming in January and February. I'd imagine the MPG loss would be even more significant without any kind of grille blocking.
 

·
Registered
Joined
·
846 Posts
Should we cover all areas where the radiator is exposed except for that one camera? What would be the best material to use that lowers the risk of it blowing off and getting to someone's windshield and still insulate against the cold? Can we use old insulated jackets instead? :)

I think with the limited / tech package, there is a camera right behind/below the toyota symbol on the hood. I just noticed it when spraying the radiator the last time it was warm enough here to get rid of the sale stuck to the radiator and the underside.
 

·
Registered
Joined
·
342 Posts
Discussion Starter #20
Should we cover all areas where the radiator is exposed except for that one camera?
So far I have covered only the upper grille area, between the headlights. I'll do half of the bottom grille area between the fog lights this week.

What would be the best material to use that lowers the risk of it blowing off and getting to someone's windshield and still insulate against the cold? Can we use old insulated jackets instead? :)
Plywood is probably a bad idea. :D I used some plastic and tape. Insulation is not required here. Just blocking air flow. You can be creative here.


https://www.google.com/search?q=grille+block+pipe+insulation
Lots of ideas using pipe insulation. Click Google images for some examples.
 
1 - 20 of 221 Posts
Top